Understanding Irritability in Relation to Anger, Aggression, and Informant in a Pediatric Clinical Population.

Objective Despite its clinical relevance to pediatric mental health, the relationship of irritability with anger and aggression remains unclear. We aimed to quantify the relationships between well-validated, commonly used measurements of these constructs and informant effects in a clinically relevant population. Method A total of 195 children with primary diagnoses of attention-deficit/hyperactivity disorder, disruptive mood dysregulation disorder, or no major disorder and their parents rate irritability, anger, and aggression on measures of each construct. Construct and informant relationships were mapped via multi-trait, multi-method factor analysis. Results Parent- and child-reported irritability and child-reported anger are highly associated (r = 0.89) but have some significant differences. Irritability overlaps with outward expression of anger but diverges from Anger in anger suppression and control. Aggression has weaker associations with both Irritability (r = 0.56) and Anger (r = 0.49). Across measures, informant source explains a substantial portion of response variance. Conclusion Irritability, albeit distinct from Aggression, is highly associated with Anger, with notable overlap in child-reported outward expression of anger, providing empirical support for formulations of clinical irritability as a proneness to express anger outwardly. Diagnostic and clinical intervention work on this facet of anger can likely translate to irritability. Further research on external validation of divergence of these constructs in anger suppression and control may guide future scale revisions. The proportion of response variance attributable to informant may be an under-recognized confound in clinical research and construct measurement.